A ball, which is full 　　   either hot air or light gas, can fly 　　   the sky.

The rocket must go 　　   a speed fast enough to escape the pull 　　   the earth, otherwise it will fall back 　　   the earth.

　　   satellites, you cannot watch TV programs coming 　　   the other side　　  the world.

The problem to be discussed 　　   the meeting tomorrow is 　　 great importance.

Given the chance to go abroad 　　   business, he gladly accepted it.

Ships and planes can keep 　　   　　   the path of the hurricane.

Man-made satellites are carried up 　　   space 　　   rockets.

目的是做某事　　　　 

提出(主意、计划等)　　　　 

恢复生气，活跃起来